In recent years, a separation membrane for water treatment has attracted attention as a technology for treating water by an environmentally friendly method. This separation membrane has been applied to various water treatment fields such as domestic wastewater treatment, factory wastewater treatment, ultrapure water production, desalination of seawater, and the like. The separation membrane for water treatment is largely classified into a microfiltration membrane, an ultrafiltration membrane, a hollow fiber membrane, a nanofiltration membrane, or a reverse osmosis membrane depending on purposes, and these membranes may be mixed and used as needed.
The separation membrane for water treatment may be largely classified into a separation membrane using a cellulose-based hydrophilic polymer such as cellulose acetate, cellulose nitrate, or the like, and a separation membrane using a hydrophobic polymer such as polyethylene, polypropylene, polysulfone, polyethersulfone, polyvinylidene fluoride, polytetrafluoroethylene, or the like.
The hydrophilic polymer has activated interaction with water molecules due to hydrogen bonding, or the like, and thus water permeates easily into the hydrophilic polymer, thus resulting in high water flux. However, the hydrophilic polymer is sensitive to heat and chemicals, and has a problem in that polymer chains are easily separated by an enzyme included in a subject fluid to be treated, or the like, and thus the membrane is destroyed.
The hydrophobic polymer is generally resistant to heat and chemicals and has excellent physical properties such as mechanical strength, and the like. However, the hydrophobic polymer has problems in that water flux is remarkably low due to hydrophobicity, and the hydrophobic polymer is contaminated more easily than the hydrophilic polymers by contaminants such as proteins and the like. In order to solve these problems of the hydrophobic polymer, various methods such as a method of including inorganic particles such as titanium dioxide or the like, a method of treating a functional group such as a carboxyl group on a surface of a separation membrane, and a method of treating a hydrophilic polymer such as polyvinyl alcohol or the like, at the time of preparing the separation membrane, have been proposed. However, these methods still have problems in that water flux is low due to relatively low hydrophilicity of the separation membrane, and the separation membrane is vulnerable to contamination.
Korean Patent No. 10-0994178 also discloses a polyethersulfone composite membrane including titanium dioxide particles, but has a problem in that since hydrophilicity of the composite membrane prepared by mixing the titanium dioxide particles is only partially improved, water flux is still low for application to a large amount of water treatment at a time.